Hot gas gun



Oct. 1, 1957 c. J. O'BRIEN 2,808,254

HOT GAS GUN Filed April 6. 1953 United States Patent ice HOT GAS GUN Charles J. OBrien, Lockport, N. Y., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application April 6, 1953, Serial No. 346,879

2 Claims. (Cl. 263-19) The present invention relates to means for generating hot gases and more particularly to a hot gas gun for generating a large volume of gas having a moderate temperature.

Certain materials such as thermoplastic substances may be softened by the application of heat so that they may be easily worked into any desired shape. Also thermalsetting plastics such as are frequently employed in bonding several objects together require the application of heat to cause the plastic to set or cure. Heretofore, it has been necessary to place the plastic in an oven or to utilize a torch for heating the plastic. If an oven is used to heat the plastic, any structure attached thereto is heated. This heat may soften and deform other plastic members or otherwise impair the usefulness of the structure. If a gas torch is employed it is possible to heat localized areas of the structure so as to treat only the portion of the structure desired. However, the gas torches presently employed generally produce a flame having such a high temperature that a great deal of care must be exercised to prevent injury by burning or otherwise overheating the plastics.

It is proposed to provide a hot gas gun for treating plastics which has a combustion chamber for burning gaseous fuels having relatively high combustion temperatures. In order to prevent overheating of the object to be treated, a cooling jacket is placed in heat exchanging relation with the combustion chamber so that cooling fluids may pass through the jacket and cool the products of combustion produced by the burning of the fuels. This will not only cool the products of combustion but will also heat the cooling fluid. Thus the cooled products of combustion may be used as a reducing atmosphere to heat plastics or other material or if desired the cooling fluids may be used as an oxidizing atmosphere for heating. Also the gun may be used to produce a large volume of moderately hot gas by combining the cooling fluids with the burning gases.

Heretofore, the temperature generated by a gas torch can only be varied by varying the amount of gas that is burned. When the volume of gas varies the flame characteristics are very apt to be injuriously aflected unless the tip of the torch is changed. Also when the volume of gas is reduced, the amount of heat available will be decreased as the temperature drops.

It is therefore proposed to provide a torch in which the temperature of the exhaust gases may be varied while at the same time producing substantially the same amount of available heat. This is accomplished by placing a cooling jacket about the combustion chamber so that the temperature of the combustion can be varied by merely controlling the flow of cooling fluid. By mixing the cooling fluids with the products of combustion, the fuels may be burned at an eflicient temperature. Also the temperature of the exhaust gases may be lowered without reducing the amount of available heat.

In the drawings:

Figure 1 is a side elevational view, having a portion thereof broken away, showing a hot gas gun embodying the present invention.

Figure 2,is a side elevational view similar to that of Figure 1 but showing a modification of the present invention.

Figure 3 is a cross-sectional view taken substantially along the plane of line 3-3 of Figure 2 and showing the inlet end or" the modified hot gas gun.

Figure 4 is a cross-sectional view taken substantially along the plane of line 44 of Figure 2 and showing the outlet end of the modified hot gas gun.

Figure 5 is a side elevational view, having a portion thereof broken away, of a further modification of the present invention.

Referring to the drawings in more detail, the hot gas gun has an elongated tubular member 12. An opening 14 extends longitudinally through the tubular member 12' to form a combustion chamber 16 which is of substantially cylindrical shape. A plug 18 is secured in position across the inlet end 20 of the tubular member 12 by any suitable means. An aperture 22 is provided through the plug 18 and threadably receives the outlet end 24 of a fuel line 26. Passages 25 are provided in plug 18 to admit the air needed for combustion of the fuel. The fuel line 26 may be connected to any convenient source of fuel such .as compressed illuminating or'acetylene gas. The outlet end 24 of the fuel line 26 is disposed in the combustion chamber 16 and may be of any form suitable to deliver the fuels to the chamber 16 for combustion therein.

The outlet end 28 of the combustion chamber 16 may comprise a neck 3%) on the end of the tubular member 12 and a nozzle 32 secured in the small end 34 of the neck 36. The nozzle 32 is adapted to discharge the hot exhaust gases from the combustion chamber 16 onto the plastic or any other material that it is desired to heat. The nozzle 32 may be given a cross-sectional size and shape which will cause the hot exhaust gases to flow at the optimum velocity and in the best pattern. If desired the nozzle 32 may be threaded into the end 34 of the tubular member 12 to permit changing the nozzle 32 for varying work conditions. a

To reduce the temperature of the hot exhaust gases created by the burning fuel to a point where the plastic or other material can not be damaged by overheating, means may be provided for placing cooling fluids in heat exchanging relation with the combustion chamber 16. In the present instance a jacket 36 is disposed about the exterior of the tubular member 12 in spaced relation thereto. The jacket 36 comprises a pair of rings 38 and 49 and a sleeve 42 having a shape similar to that of the tubular member 12. The rings 38 and 40 are disposed at opposite ends of the sleeve 42 and are secured to the shank 44 and the end 34 of the tubular member 12. It is thus apparent that the space 46 between the sleeve 42 and the tubular member 12 forms an envelope 48 that.

is sealed from the atmosphere and completely encompasses the tubular member 12. Due to the heat conductivity of the tubular member 12, any gases in the envelope 48 will be in heat exchanging relation with the hot gases in the combustion chamber 16.

Inlet means 56 may be positioned in one end of the sleeve 42 to deliver a cooling fluid into the envelope 48 formed by the jacket 36. The cooling fluid may be either liquid or gaseous such as compressed air or an inert gas.

During operation of the gun 10, as the gases are burned,

heat will be transferred from the combustion chamber" fuel. If a reducing atmosphere is desired for heating the ,v object to be treated, the cooled products of combustion latented Oct. 1, 19 ,7

, the jacket 36,, it can be applied to the object to be heated. In the present instance it is desired to obtain a maximum volume of hot gases. Accordingly, a plurality of outlet passages 52 are circumferentially spaced about the neck 30 so as to interconnect the fluid envelope 48 with the combustion chamber 16, preferably adjacent the discharge nozzle 32. The passages 52 are diagonally disposed so that the heated cooling fluids will be injected into the exhaust gases and thoroughly mixed therewith. This willproduce a homogeneous mixture containing the cooling fluids and products of combustion. Thus a large volume of,gas having a moderate temperature is available for heating the plastics. It is quite apparent that by merely varying the volume of the combustible gases and the cooling fluids flowing through the jacket 36 any desired volume of gases at any desired temperature may be obtained.

' The hot gas gun may be embodied in a modified form to provide a more complete transfer from the combustion chamber to the jacket. T he embodiment of the gun 54 shown in Figure 2 may have a tubular member SG'that forms a substantially cylindrical combustion chamber 58 similar to that in the first embodiment. The inlet end 60 of the combustion chamber 58 may be sealed by a plug 62 that is secured to the tubular member 56 by any suitable means so that the plug 62 projects from the end 60 of the tubular member 56. The plug 62 may be pro vided with an aperture 64 for threadably receiving the end of the fuel line 66. Although the fuel line 66 may be identical with that in the preferred form, a perforated grate'68 or other means may be provided adjacent the outlet end of the fuel line 66 so as to disperse the combustible fuel throughout the combustion chamber 58 to thereby provide any desired flame shape. In order to provide a more complete and eificient burning of the fuel a plurality of secondary passages 70 may be provided through the plug 62. These passages 70 communicate between the atmosphere and the inlet end 60 of the combustion chamber 58, It is desirable that the passages 70 be positioned so that the draft from the fire will draw air into the combustion chamber 58 similar to a Bunsen burner. The outlet end 72 of the chamber 58 may have a neck 74 and a detachable discharge nozzle 76 similar to that in the first embodiment 10.

A jacket 78 comprising a sleeve 80 which is substantially the same length as the combustion chamber 58 is spaced concentrically about the tubular member 56. A pair of attaching rings 82 and 84 are secured to the opposite ends of the sleeve 80 and are mounted on the outer "end of the plug 62 and the neck 74 adjacent the discharge nozzle 76. Thus it is apparent that this will form an envelope 86 that completely encases the tubular member 56 and is sealed from the atmosphere. Inlet means SS, which may also be identical to that of the first embodiment are provided in the sleeve 80 so as to discharge cooling fluids into the envelope 86. This will cause the cooling fluids to flow along the surface of the tubular member 56 in heat exchanging relation with the combustion chamber 58. This will heat the cooling fluids and cool the hot exhaust gases the same as in the first embodiment 10; however, due to the increased areas exposed to the cooling fluid, the transfer of heat will be i bustion chamber SMWith a necked downoutlet end 96 substantially the same as previously described. The inlet end 98 of the combustion chamber 94 may be similar to either the first or second embodiment. 100 similar to that of the second embodiment is employed, however no grate is used. The cooling jacket 102 comprises a sleeve 104 mounted on ring members 105 and 167 similar to that of the second embodiment 54, although it may be identical with that of the first embodiment 10. Since it is desirable to obtain a more complete transfer of heat in this embodiment, a baffle 106 is placed in the fluid envelope 108 formed by the space between tubular member 92 and the sleeve104 so as to form a tortuous path 110. This baffle 106 may comprise a helix integral with the tubular member 92 so as to make the envelope 108 in the form of a spiral path 110. This not only effectively increases the area of contact for heat transfer, but it also requires the cooling fluid to follow a longer path and thereby remain in contact with the tubular member 92 for a longer period.

The heated cooling fluids may be mixed with the products of combustion as previously described or else used directly for heating the object to be treated. In thisrembodiment a separate outlet 112 in the form of a duct 114 is employed for allowing the cooling fluids to be released from the' jacket 102. Thus the hot exhaustproducts formed by the burning fuels may be cooled without mixing them with the cooling fluids. This allows a liquid coolant to be used if desired and also permits the reducing atmosphere of the cooled exhaust gases to be used for heating the object to be treated. Also if it is desired to heat the object in an atmosphere that is not contaminated by the products of combustion the duct 114 may be used. Thus an atmosphere of inert or oxidizing gases may be employed for heating the object by the choice of a proper cooling fluid.

While three embodiments have been shown and described, it will be apparent to those skilled in the art that the invention may be embodied in other forms without departing from the spirit thereof. It is also apparent that While each embodiment has distinctive features such as the baffie, the inlet means, the outlet means,

etc., these features are interchangeable, and therefore the features of one embodiment may be added to or removed whenever it is desired. It is therefore to be understood that the present embodiments are merely illustrative and in no way restrictive, and that it is intended to limit the invention only by the scope of the claims which follow.

What is claimed is: V

l. A hot gas gun comprising a tubular member having walls disposed to form an elongated combustion chamher, said combustion chamber having an inlet passage associated with one end thereof for admitting fuel to said combustion chamber and an outlet passage at the other end thereof including a neck for discharging the products of combustion from said chamber through a nozzle and into the atmosphere, and a cooling jacket completely surrounding and spaced from said elongated combustion chamber to provide a continuous cooling chamber around 7 said tubular mernber, said cooling chamber being closed at both ends thereof and said cooling chamber having an inlet passage therein at the same end of said gun as said fuel inlet passage for admitting coolant fluid under pres sure between said cooling jacket and said tubular member and coolant fluid outlet passages for introducing said cooling fluid into the stream of combustion products, said coolant outlet passages comprising circumferentially spaced openings in the smaller end of said combustion chamber neck and being disposed radially about and obliquely to the axis of said combustion chamber.

2. A hot gas gun comprising a tubular member having Walls disposed to form an elongated combustion chamber, s aid combustion chamber having an inlet passage associated with one end thereof for admitting fuel to said combustion chamber and an outlet passage at the other end thereof. for discharging the products of combustion from'said chamberinto the atmosphere, and "a An inlet plug cooling jacket completely surrounding and spaced from said elongated combustion chamber to provide a continuous cooling chamber around said tubular member, said cooling chamber being closed at both ends thereof and said cooling chamber having an inlet passage therein at the same end of said gun as said fuel inlet passage for admitting coolant fluid under pressure between said cooling jacket and said tubular member "and coolant fluid outlet passages for introducing said cooling fluid into the stream of combustion products, said coolant outlet pas sages comprising circumferentially spaced openings in the wall of said combustion chamber at the exhaust outlet end thereof and being disposed radially about and obliquely to the axis of said combustion chamber and sloping inwardly in the direction of said combustion chamber outlet passage.

References Cited in the file of this patent UNITED STATES PATENTS 1,700,142 Searle Jan. 29, 1929 2,185,886 Caldwell Jan. 2, 1940 2,396,968 Phillips Mar. 19, 1946 2,502,947 Hess Apr. 4, 1950 2,583,736 Hess Jan. 29, 1952 FOREIGN PATENTS 342,874 France Sept. 20, 1904 

